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NEET levelSingle correct optionDifficulty 1 of 3g2008

Which of the following is the strongest acid in water?

Aphenol ( $C X_{6} H X_{5} OH$ )
Bacetic acid ( $CH X_{3} COOH$ )
Cbenzenesulfonic acid ( $C X_{6} H X_{5} SO X_{3} H$ )
Dethanol ( $C X_{2} H X_{5} OH$ )

Answer: C

The benzenesulfonate ion spreads its negative charge over three oxygen atoms, and sulfur is strongly electron withdrawing. Sulfonic acids (pKa below 0) are therefore much stronger than carboxylic acids (pKa about 4-5), phenol (10) and ethanol (15.9).

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